Physical Science 101
Global Warming

Global Warming

Is the world actually getting warmer?
IPCC 2007: Climate Change 2007: The Physical Science Basis.


Global temperature is an average of all temperature record measurements.
Historical records - municipal/state/federal records - amateur records and diaries
Limited span of time for which these records can be used.
Temperature: 1880 to 2006.

Proxy Temperature Records

Data from sources which do not give actual temp. - inferred temperature
Biological Proxy Records:
Geological Proxy Records:
Chemical Proxy Records:
Benthic Foraminiferal Stable Isotope Data Graph: 1 million b.p. to Present.
Entire Earth History Temperature Graph: 4.6 billion b.p. to Present.

Glacial Ice Mass Balance Measurements

Glaciers form from the long term accumulation of snow and ice.
Ocean water is the primary source of water found in glaciers
During climatic cold periods glaciers form:
During climatic warm periods glaciers melt:
Glacier Mass Balance Graph: 1960 to 2000.

Sea-Level Measurements

Sea level is not constant
Changes on a daily basis:
Changes on an annual basis:
Causes of eustatic changes in sea level:
Sea Level Change Graph: 1880 to Present.

The Causes of Climate Change

Natural Causes
Human Induced Causes

Solar Radiation

The sun is the main source of energy for processes at the Earth's surface
It is the driving force for life, atmospheric circulation, ocean circulation, weather, climate.
Changes in the amounts of incoming radiation vs. outgoing radiation will result in global warming or cooling.

Orbital Parameters

Variations in the amount of solar radiation received on Earth due to variations in three orbital parameters.

Axial tilt

Axis is tilted relative to the ecliptic - 23.5 degrees (23°27') from a perpendicular to the ecliptic
The axial tilt varies from 22° to 24.5°.


The axis completes one precession in 25,800 yrs

Orbital Eccentricity

The Earth's orbit is an elliptical path .
Eccentricity: a measure of how much an ellipse deviates from a circle
Earth's Eccentrisity Variations.

Milankovitch Cycles

Cycles in the amount of solar radiation received on Earth due to variations in orbital parameters.

Relationship between Insolation and Glaciation.

Greenhouse Effect

A system in which shortwave radiation is allowed to enter freely and is absorbed, then is re-radiated as longwave radiation. The longwave radiation is then retained within the system.
Important greenhouse gases:

Human Induced Causes

CO2 Trends
CH4 Trends

Future Predictions

Sea Level